EComment. Two internal mammary artery grafts are better than one

Abstract

We read with great interest the paper by Smith et al. regarding the long-term survival benefit of the usage of bilateral internal mammary artery (BIMA) grafts in coronary revascularization surgery [1]. They included in their results 13 follow-up studies published after 2001. However, we found one additional relevant article investigating the long-term outcomes associated with BIMA grafting compared with single internal mammary artery (SIMA) among diabetic patients [2]. We would like to take this opportunity to briefly extract the relevant information from the above-mentioned study and to add a short comment on this salient subject. Puskas et al. [2] conducted a retrospective cohort analysis by extracting data from the Society of Thoracic Surgeons database at a single referral academic centre. They included a total of 3527 coronary artery bypass grafting procedures (BIMA n = 812, SIMA n = 2715). After adjustment for differences between groups by the Cox model, BIMA grafting portended a 35% reduction in the hazard of long-term death at 8 years of follow-up (adjusted hazard ratio, 0.65; 95% CI, 0.48 to 0.88, P = 0.006). The authors concluded that the usage of BIMA grafting provides significant benefit in late survival compared with SIMA grafting in both diabetic and non-diabetic patients. BIMA grafting should be performed whenever patient risk factors and comorbidities allow an acceptable risk of deep sternal wound infection. As rightly outlined by the authors, all these studies are follow-up studies. However, only one randomized trial comparing these two techniques (ART Arterial Revascularization Trial) [3] is currently under way in Europe that can broaden our understanding. ART primary outcome is survival at 10 years; therefore the results should be available by 2018. Until that date the debate will continue. This uncertainty has been reflected in the rate of adoption of BIMA grafting, the rate of use of the technique varies from 4% in North America to 10% in Europe [4]. The major reasons for not using BIMA grafts are the lack of solid evidence of benefits and the increased rate of sternal wound infection, particularly in diabetics. Of note, in the SYNTAX study [5], BIMA grafting was used in a relatively higher percentage of 28% of patients. The more liberal use of BIMA in this trial entails a paradigm shift in grafting strategies worldwide.